APS systems provide pedestrian signal indications in a non-visual format such as: audible (e.g. sounds, tones, verbal messages, etc.) or vibrotactile (e.g. vibrating raised pushbutton surface) formats. APS systems may generate different types of signal indications for different applications. For example, APS systems typically have different audible “walk” indications for east-west and north-south crossings, in addition to pole locator tones, wait tones, and the like. It is important that APS systems provide correct pedestrian signal indications to protect the safety of visually impaired or visually and hearing impaired pedestrians.
A traffic light control system typically incorporates a malfunction management unit (MMU) which monitors traffic signal channels for conflicting inputs and invalid signal voltage levels and the like, and responds to a detected failure or abnormal condition. As conventional MMUs are designed for traffic control systems which provide basic visual traffic signal information, such MMUs may generally lack the control to reliably recognize and respond to conflict or error in non-visual pedestrian signal indications as generated by APS systems, and particularly, with respect to multiple types of audible indications for different applications.
There is a general desire to provide conflict monitoring and error detection for APS systems. There is a general desire to provide APS systems incorporating conflict monitoring and error detection which may be retrofit into existing traffic control systems.